Calculation of heat flux and evolution of equivalent thermal contact resistance of carbon deposits on Tore Supra neutralizer

This paper presents a new heat flux computation applied to the neutralizer of Tore Supra using a deconvolution procedure and the thermal quadrupoles method. A steady deposition of carbon takes place at a rate of about 30 nm/s on the actively cooled carbon fibre composite (CFC) surface of the neutralizer. Thermal measurements of the surface temperature are available through optical fibre-based infrared thermography. These measurements are used to estimate the heat flux and to follow the temporal evolution of a single parameter, representing the thermal properties of the growing thin carbon layer. This parameter corresponds to an equivalent thermal resistance Req (in m2 K W−1). During the first 2000 s of plasma operation on a new CFC neutralizer surface, Req rises about proportionally with exposure time. From then on no significant further evolution of Req is observed. We interpret this as indication for a thermal and mechanical detachment of the deposit from the substrate for deposits exceeding a thickness of 60 μm.